The invention is directed to a sewing or embroidery machine with an embroidery module having an embroidery frame drive unit for driving differently sized interchangeable embroidery frames.
The embroidering of sewing material which is fixed in an embroidery frame and can be driven in X- and Y-directions by a drive unit is known. In embroidery machines, the drive unit is frequently a portion of the lower arm; in household sewing machines, the drive units, also termed embroidery modules, are held, docked in a play-free manner, on the sewing machine, i.e., on the lower arm and/or the baseplate. The connection between the embroidery frame and the drive unit takes place through an embroidery frame support which is connected to the drive elements in the drive unit, and holding and locking devices on the embroidery frame.
It is further known to arrange on the embroidery frame, impulse generating means, e.g., indentations, curves or bar codes, etc., with which the docked embroidery frame can be identified by the machine control (DE 29612102 U1) and/or with which the docking place can be identified on an embroidery frame (U.S. Pat. No. 6,237,516 B1), when plural docking places are present (DE 31 30 371 A1). Besides the unambiguous identification of the docked embroidery frame, the impulse generating control means also serve in DE 29612102 to indicate to the operator, on a display on the sewing machine, which embroidery frame (e.g., round, oval, square, etc.) is docked and in addition, at which docking place on the embroidery frame this has occurred. The information regarding the docking place also lets the operator know which sewing region within the embroidery frame can be embroidered. The pattern to be embroidered on the relevant sewing region can also be shown on the display.
It is therefore known from DE 29612102 to provide on the drive unit an identification of the kind and size of the docked embroidery frame, and to graphically display on a display device the sensed data relating to the kind and size of the embroidery frame. Furthermore, it is possible to determine, by means of the central machine control device, the desired relative position of the embroidery frame in relation to the needle and the stitch hole, and later to start the embroidery process from this reference position.
Thus the kind and size of the embroidery frame, and also the location of docking on embroidery frames with plural docking places, can be determined and therewith the relative position of the embroidery frame in relation to the needle. However, it is not possible to sense faults in the drive system, when for example steps of the stepping motor have been lost for any reason and consequently the embroidery frame support is not located at the desired position.
The present invention therefore has as its object to provide a sewing or embroidery machine with a drive unit for an embroidery frame, with which drive unit there can be determined, not only the kind and size of the embroidery frame and the docking position on the embroidery frame, but in addition the exact present position of the embroidery frame with respect to the drive unit, and thereby to the needle position.
This object is attained by a sewing or embroidery machine having a reference element located on the embroidery frame for each impulse generating or triggering means connected to the drive unit as a control means. This compares the actual reference location sensed by the sensor of the reference element to the desired position of the embroidery frame in the holding device. Advantageous embodiments of the invention are defined in the dependent claims.
The arrangement of one or more reference points on the embroidery frame are situated respectively at a precisely defined distance from a reference zero point on the drive unit which makes it possible on the one hand to determine the exact position of the embroidery frame in relation to the reference zero point, and on the other hand also to determine whether the embroidery frame is correctly connected to the embroidery frame support, or to determine whether an embroidery frame is in fact docked to the embroidery frame support. With the knowledge of the exact present position with respect to the reference zero point, even when a deviation occurs, e.g., due to lost steps of the stepping motor in the drive unit, a correction can be automatically performed with the machine control, or the beginning of embroidery can be prevented. This makes it possible to guide and produce embroidery subjects over a surface extending over the embroidery region, without the positioning and subsequent points on the previously embroidered areas being visible after displacement of the embroidery frame.